The present disclosure relates to a plastic sheet on which text or images are marked by laser marking and to a booklet including such plastic sheets as booklet pages.
Plastic sheets on which text or images are marked by projection of a laser beam have been proposed. Such a plastic sheet allows text or images to be marked at an inner part of the plastic sheet when the focal point of the laser beam is controlled to be at the inner part of the plastic sheet (for example, see International Publication No. 2012/008278).
To mark text or images at an inner part of the plastic sheet by projection of a laser beam, an amount of energy that changes the property of part of the material of the plastic sheet is necessary. For this reason, time is required for the energy of the laser beam projected onto the plastic sheet to reach a level that changes the property of part of the material in order to mark predetermined text or images on the plastic sheet.